Motor controller

ABSTRACT

A motor controller is made up of a power supply circuit rectifying an AC power supply for outputting desired DC voltages while, at the same time, improving the power factor of the AC power supply, and a motor drive circuit for driving a motor. The controller has a rectifier circuit for converting AC power to a DC voltage and a smoothing circuit, a converter circuit constituted of a chopper circuit for controlling the DC voltage by utilizing a switching operation and the energy storing effect of an inductance, a motor drive device made up of an inverter circuit connected to the output of the converter circuit to control a motor, a converter control circuit for controlling the switching operation of the chopper circuit, an inverter control circuit for controlling the switching operation of the inverter circuit thereby driving the motor, a speed detector circuit for detecting a position of the rotor of the motor for calculating the speed of the motor, a speed control circuit receiving the calculated speed value and a speed command value for controlling the motor speed through the inverter circuit, and a DC voltage control circuit receiving the output signal of the speed control circuit for controlling the DC voltage through the converter control circuit in accordance with the output signal. The DC voltage control circuit, when the output of the speed control circuit reaches a predetermined value, outputs a signal to cause the DC voltage to increase or decrease to the converter control circuit. The output of the speed control circuit is a duty ratio signal or a speed deviation signal representing a deviation of the calculated speed value from the speed command value.

BACKGROUND OF THE INVENTION

The present invention relates to a motor controller made up of a powersupply circuit for rectifying an AC power source to output desired DCvoltages while, at the same time, improving the power factor of the ACpower source, and to a motor drive circuit for driving a motor.

A motor controller operating as a rectifying circuit for rectifying anAC power source to provide a DC power supply and for performing speedcontrol of a motor by using, in combination, a power supply circuit,which is capable of suppressing harmonics occurring in the power sourcecurrent, and a motor driving circuit is disclosed in Japanese Laid-openPatent No. Hei 6-105563 is known.

The motor controller is formed of a power factor improving convertercircuit employing a step-up chopper circuit, which simultaneouslyperforms suppression of harmonics in the power source current andcontrol of the DC voltage, and an inverter circuit for driving themotor. The motor controller, at the time of low load operation, controlsthe DC voltage to take on the lowest voltage value which will allow thepower factor to be improved and performs speed control of the motorthrough PWM control by the inverter circuit and, at the time of highload operation, stops the PWM control performed by the inverter andperforms speed control of the motor through DC voltage control by theconverter circuit, i.e., PAM control.

In the above described motor controller, the configuration of the motorspeed control circuit at the time of low load operation and that at thetime of high load operation is different, and so different speedcontrolling operations are necessary according to the conditions of theload. Namely, at the time of low load operation, the duty ratio of thePWM signal for the inverter is calculated from the speed deviation and,at the time of high load operation, the DC voltage command for theconverter is calculated from the speed deviation.

Further, switching between the control circuit at the time of low loadoperation and the control circuit at the time of high load operation iscarried out in accordance with the DC voltage value of the duty ratio ofthe PWM signal for the inverter, the speed command value and the presentspeed.

Thus, in the above described motor controller, it is required to havetwo kinds of speed control circuits, one for low load operation andanother for high load operation, and hence, the control circuit becomescomplex.

Further, since the determination of switching of the condition for thecontrol circuits between the low load operation and high load operationis based on a number of different signals, many detector circuits arerequired.

An object of the invention is to solve the above described problemsinherent in the known motor controller and to provide a motor controllercapable of executing motor speed control by the use of one simple speedcontrol circuit, whether the load is high or low.

SUMMARY OF THE INVENTION

The present invention relates to a motor controller comprising arectifier circuit for converting AC power to DC power and a smoothingcircuit, a converter circuit constituted of a chopper circuit forcontrolling the DC voltage by utilizing switching operation and theenergy storing effect of an inductance, a motor drive device made up ofan inverter circuit connected between the output of the convertercircuit and a motor, a converter control circuit for controlling theswitching operation of the chopper circuit, an inverter control circuitfor controlling the switching operation of the inverter circuit fordriving the motor, a speed detector circuit for detecting the positionof the rotor of the motor for calculating the speed of the motor, aspeed control circuit responsive to a calculated speed value and a speedcommand value for performing speed control of the motor through theinverter control circuit, and a DC voltage control circuit responsive tothe output signal of the speed control circuit for controlling the DCvoltage through the converter control circuit.

As a preferred embodiment, the DC voltage control circuit is adapted tooutput to the converter control circuit a signal causing the DC voltageto increase or decrease when the output of the speed control circuitreaches a predetermined value.

As a preferred embodiment, the DC voltage control circuit is adapted tocontrol the DC voltage through the converter control circuit such thatthe output of the speed control circuit takes on a predetermined value.

As a preferred embodiment, a duty ratio signal or a speed deviationsignal representing a deviation of the calculated speed value from thespeed command value is provided as the output of the speed controlcircuit.

As a preferred embodiment, the motor controller further comprises a DCvoltage pulsation correcting circuit for detecting pulsating componentsof the DC voltage for changing the input signal to the inverter controlcircuit in accordance with the pulsating components.

In the above described structure, the inverter control circuit drivesthe switching device of the inverter to drive the motor in accordancewith a position signal received from the speed detector circuit and theduty ratio signal received from the speed control circuit. The speeddetector circuit detects an induced voltage by the motor and calculatesthe position of the rotor from the induced voltage to output thedetected position signal in a pulse form and, at the same time,calculates the speed from the calculated position signal to output thesame as the detected speed value to the speed control circuit. The speedcontrol circuit calculates the duty ratio signal of the PWM pulse forthe inverter from an external speed command and the detected speed valueso that the speed deviation becomes zero. The inverter circuit, motor,speed detector circuit, inverter control circuit, and the speed controlcircuit constitute a motor speed control circuit, and speed control ofthe motor is executed in accordance with the external speed command. Theconverter control circuit controls the switching device of the choppercircuit in accordance with the signal from the DC voltage controlcircuit. The DC voltage control circuit detects the DC voltage and theoutput signal of the speed control circuit, for example, the duty ratiosignal, and controls the DC voltage such that the DC voltage rises by apredetermined amount when the duty ratio signal reaches a predeterminedvalue, for example, the upper limit value of a range of the duty ratiosignal, and such that the DC voltage falls by a predetermined value whenthe duty ratio signal reaches a lower limit value. The convertercircuit, converter control circuit, and the DC voltage control circuitconstitute a DC voltage control circuit of the converter and the DCvoltage is controlled thereby.

By combining the motor speed control circuit with the converter DCvoltage control circuit and allowing both the circuits to operaterespectively, speed control of the motor can be achieved by the use of asimple structure irrespective of the load conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a motor controller according to a firstembodiment of the invention, and FIG. 2 is a schematic circuit diagramshowing the configuration of a DC voltage control circuit, which is aconstituent of the motor controller.

FIG. 3 and FIG. 4 are timing diagrams showing operations of the motorcontroller according to the first embodiment of the invention.

FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are schematic circuit diagramsshowing other configurations of a DC voltage control circuit capable ofuse in the motor controller according to the first embodiment of theinvention.

FIG. 9 and FIG. 10 are timing diagrams of the operations of the motorcontroller according to the first embodiment of the invention for thosecases where the DC voltage control circuits shown in FIG. 7 and FIG. 8are used, respectively.

FIG. 11 is a schematic circuit diagram showing another configuration ofthe DC voltage control circuit forming a constituent of the motorcontroller according to the first embodiment of the invention.

FIG. 12 is a block diagram of a motor controller according to a secondembodiment of the invention; and FIG. 13 is a schematic circuit diagramshowing the configuration of a DC voltage control circuit forming aconstituent of the motor controller.

FIG. 14 is a block diagram of a motor controller according to a thirdembodiment of the invention, and FIG. 15 is an operational diagramshowing the correcting of a pulsation of the DC voltage as performed inthe motor controller.

FIG. 16 is a block diagram of an air conditioner to which the motorcontroller of the invention is applied.

FIG. 17 is a schematic circuit diagram showing the configuration of aconverter module wherein a portion of the constituents of the motorcontroller of the invention are modularized.

BEST MODE FOR CARRYING OUT THE INVENTION

A detailed description of the invention will be given with reference tothe accompanying drawings.

FIG. 1 and FIG. 2 are directed to a first embodiment of the motorcontroller of the invention. FIG. 1 is a general block diagram of themotor controller comprising a converter circuit, which employs arectifier circuit and a step-up chopper circuit, and a motor drivingcircuit formed of an inverter circuit and a motor.

An AC power source 1 is connected to a converter circuit 2, whichoutputs a DC voltage. The converter circuit 2 is made up of a rectifiercircuit and a step-up chopper circuit, which is formed of a reactor, adiode and a transistor. The step-up chopper circuit in the convertercircuit 2, as seen in FIG. 17, for example, is connected to the outputside of the rectifier circuit 101 therein and forces the input currentto flow by the switching action of the transistor 104 and energy storingeffect of the reactor 102 to thereby step up the voltage. The stepped upDC voltage is supplied to a smoothing capacitor 105 and a stabilized DCvoltage is output therefrom.

An inverter 3 for driving a synchronous motor 4 is connected to thesmoothing capacitor within the converter circuit 2 and converts the DCvoltage supplied from the smoothing capacitor into desired AC voltagesto drive the synchronous motor 4.

A speed detector circuit 5 calculates the position of the magnetic polefrom the induced voltage produced by the synchronous motor 4 and outputsa position signal to an inverter control circuit 6. It further performsa speed calculation on the basis of the calculated position signal andoutputs a detected speed value to a speed control circuit 7.

The speed control circuit 7, on the basis of the detected speed valuereceived from the speed detector circuit 5 and an external speedcommand, outputs a duty ratio signal to the inverter control circuit 6so that the speed deviation becomes zero.

The inverter control circuit 6, on the basis of the detected positionsignal received from the speed detector circuit 5 and the duty ratiosignal received from the speed control circuit 7, generates a drivesignal to drive a transistor in the inverter 3 to thereby perform speedcontrol of the synchronous motor 4.

A converter control circuit 8 drives the transistor within the convertercircuit 2 in accordance with a current command value received from a DCvoltage control circuit 9 and controls the input current to theconverter circuit 2 to have a sine wave form to thereby improve thepower factor of the power source and control the DC voltage at the sametime.

The DC voltage control circuit 9 detects the duty ratio signal output bythe speed control circuit 7 and controls the DC voltage in accordancewith the value of the duty ratio signal.

FIG. 2 shows an example of the internal structure of the DC voltagecontrol circuit 9 according to the present invention. The DC voltagecontrol circuit 9 is formed of a selector circuit 93 and a multiplexer95 for selecting, in accordance with the duty ratio signal, one of aplurality of DC voltage command values generated by a DC voltage commandvalue generator circuit 96 and for outputting the selected signal, adetector circuit 94 for detecting the output DC voltage from theconverter circuit 2 and for converting the same into a voltage value ata level usable in the control circuit 2, a proportional term 91, and anintegral term 92.

The proportional term 91 and the integral term 92 operate so that thedeviation of the dc voltage detection value from the DC voltage commandvalue may become zero and outputs the result as a current command.

The multiplexer 95 is a circuit which operates to select one of theplurality of provided DC voltage command values in accordance with anexternal signal and outputs only the selected DC voltage command value.In the example shown in FIG. 2, the DC voltage command values from 1 to4 are arranged in ascending order of the value. The DC voltage commandvalue 1 is set to the lowest DC voltage that is controllable by theconverter circuit 2.

The selector circuit 93, upon receipt of the duty ratio signal from thespeed control circuit 7, outputs a switch signal corresponding to thevalue of the duty ratio signal to the multiplexer 95.

The operation of the selector circuit 93 will be described withreference to FIG. 3, which is an explanatory drawing of the controloperation. FIG. 3 is a graph with the number of revolutions of the motortaken along the abscissa and the DC voltage, the motor voltage and theduty ratio taken along the ordinate. The graph shows variations of themotor voltage, DC voltage and duty ratio with respect to the number ofrevolutions under a constant load.

At the time when the motor is rotated at a low speed, such as when it isstarted up, the selector circuit 93 outputs a switch signal to cause theDC voltage command value 1 to be selected and the DC voltage controlcircuit 9 controls the DC voltage to take on the selected DC voltagecommand value 1.

Since the voltage is low in this state of the controlled DC voltage, theduty ratio reaches 100% at an early stage of the increase in therotating speed and, hence, it becomes impossible to increase the numberof revolutions of the motor any more (point A). At this point, theselector circuit 93 outputs a switch signal to select the DC voltagecommand value 2 to the multiplexer 95. The multiplexer 95 selects the DCvoltage command value 2 and the DC voltage control circuit operates suchthat the DC voltage takes on the DC voltage command value 2. Thereby,the duty ratio is suddenly lowered to 60%, while the motor voltage isincreased. Although, in the case shown, the minimum value of the dutyratio is set to 60%, this is a value used for convenience ofexplanation. In reality, depending on the load condition, the number ofrevolutions of the motor, the response speed of the speed controlcircuit 7 and the like, the duty ratio does not exhibit a sharp change.

As the number of revolutions of the motor increases, the duty ratiobecomes 100% again (point B). Then, the operation as described above isperformed again to select the DC voltage command value 3, whereby the DCvoltage is increased and the duty ratio again is lowered to 60%.

Through repetition of the above described operations, the DC voltage isincreased with the increase in the number of revolutions and, thus,speed control of the motor can be executed.

The case of decreasing the speed of the motor contrary to the above willbe described below.

When the number of revolutions of the motor is decreased upon receipt ofa speed reducing command, while the motor is rotating at a high speed,the duty ratio is decreased and the motor voltage is lowered. When theduty ratio becomes 60% (point C), the DC voltage-command value isswitched from the DC voltage command value 4 to the DC voltage commandvalue 3, contrary to the above, and, thereby, the DC voltage is lowered.When the DC voltage is lowered, the duty ratio is increased to take on avalue close to 100%. Here, the decrease in the DC voltage must be set tosuch a value that will not cause the duty ratio to exceed 100% when theDC voltage is lowered.

To decrease the number of revolutions further, the duty ratio isdecreased and the DC voltage command value is switched from the DCvoltage command value 3 to the DC voltage command value 2 at the pointB. By repeating such operations, the number of revolutions of the motoris controlled.

Through repetition of the above described operations, the duty ratio iskept close to 100% at all times and the motor voltage can also be keptclose to the voltage required by the motor at all times. Thus, theconditions of the motor and the inverter can be improved in terms oflosses incurred therein and the motor can be driven with a goodefficiency and the inverter efficiency kept at a good level at alltimes. Further, as for the converter, the DC voltage need not be raisedmore than necessary and, hence, the converter efficiency can beimproved.

Further, since the DC voltage can be changed according to the number ofrevolutions of the motor, one single circuit can support motor rotationfrom a low speed to a high speed. In other words, even some kinds ofmotors which have different motor design features can be supported byone controller and operated anytime at an effective operating point.

FIG. 4 is an explanatory drawing showing the controlling operations inthe case where the switching points of the DC voltage are in the rangeof higher number revolutions than in the case shown in FIG. 3. Basicoperations therein are the same as in the case of FIG. 3. The pointdifferent therefrom is that the values of the duty ratio at which the DCvoltage is switched are set to 100% and 90%.

Since a step-up chopper circuit is used in the converter circuit 2 andthe DC voltage cannot be lowered below {square root over (2+L )} timesthe received voltage, the operation shown in FIG. 4 is more effective inpractical operations than that shown in FIG. 3. Further, although theconverter circuit employing a step-up chopper circuit has been mentionedin the description of the present embodiment, the same operations can beperformed even when a converter circuit employing an up/down choppercircuit or the like and which is capable of stepping down the DC voltageis used.

In the foregoing, operations in the case of using four selection levelsof the DC voltage command values were described. However, it is possibleto set up the DC voltage command values more finely. Further, since theDC voltage can be controlled in a wider range, it is better to increasethe number of the selectable DC voltage command values as long as thecircuit configuration permits.

Although, in the case of the DC voltage control circuit shown in FIG. 2,the current command value is calculated from the deviation of the DCvoltage, the DC voltage command value may be directly calculated.

FIG. 5 is a diagram showing the internal structure of another embodimentof a DC voltage control circuit, which is different from the DC voltagecontrol circuit shown in FIG. 2. The points of difference from FIG. 2lie in a DC voltage command generator circuit 98 and a DC voltagedetector circuit 97. In the system shown in FIG. 5, there is only one DCvoltage command value and there are provided a plurality of detectorcircuits 97. The other circuits function in the same manner as those inFIG. 2.

In the case of FIG. 5, the multiplexer 95 is switched by a switch signalgenerated by the selector circuit 93 in response to receipt of a dutyratio signal and, thereby, one of the plurality of detector circuits isselected. According to the detection signal from the selected detectorcircuit, the DC voltage is controlled. Also in this system, theoperations described with reference to FIG. 3 and FIG. 4 can beperformed and the same effects can be obtained. Here, the detectorcircuit 97 is a circuit for converting the DC voltage into a voltagelevel which can be treated by the control circuit, and the circuit isconfigured such that it generates a voltage at the same level as the DCvoltage command value when a predetermined DC voltage level is reached.

Recently, many kinds of devices, such as a converter circuit controllingan IC, of the type in which the DC voltage is controlled throughadjustment of the gain in the detector circuit have been produced. Inmotor controllers employing such a converter circuit controlling an IC,the system as shown in FIG. 5 can be used effectively.

FIG. 6 is a diagram showing a more specific example of the circuit ofFIG. 5. In FIG. 6, the selector circuit 93 shown in FIG. 5 is realizedthrough software employing a microcomputer 70. Further, the proportionalterm 91 and integral term 92 shown in FIG. 5 are realized by an analogcircuit employing an operational amplifier 71. The detector circuit 97for detecting the DC voltage is constructed as a resistor ladder circuit72, as shown in FIG. 6. Here, the microcomputer 70 also performs thefunctions of the speed detector circuit 5 and the speed control circuit7 shown in FIG. 1.

The DC voltage control circuits shown in FIG. 2, FIG. 5 and FIG. 6 arecircuits for performing DC voltage control through selection of the DCvoltage command value or the DC voltage detection value by means of themultiplexer 95 or the like. In these systems, however, the command valueor the detection value is switched over discontinuously. Hence, a greatchange in the DC voltage is produced at the switching time.

FIG. 7 shows the structure of a DC voltage control circuit employing aDC voltage command calculation circuit 90 which is capable ofcontinuously varying the DC voltage command value 96 shown in FIG. 2.Further, FIG. 8 shows a case where the DC voltage detector circuit 97shown in FIG. 5 is replaced with a DC voltage detection and calculationcircuit 99.

The DC voltage command calculation circuit 90 detects the duty ratiosignal and calculates the DC voltage command value causing the dutyratio to take on a predetermined value. On the other hand, the DCvoltage detection and calculation circuit 99 detects the duty ratiosignal and calculates the DC voltage detection gain causing the dutyratio to take on a predetermined value and, then, outputs the DC voltagedetection value in accordance with the detected gain.

Through the described circuit configurations, the DC voltage commandvalue or the DC voltage detection value becomes a continuous output andallows the DC voltage to be controlled linearly.

FIG. 9 shows the DC voltage, duty ratio and the motor voltage withrespect to the number of revolutions obtained when the DC voltagecontrol circuit shown in FIG. 7 or FIG. 8 is used. According to thissystem, the DC voltage can be linearly controlled and, hence, smoothmotor control can be executed.

Since the DC voltage can be controlled to become lower than the powersource voltage when an up/down chopper circuit is used in the convertercircuit 2 shown in FIG. 1, control with a large value of the duty ratiocan be executed in the range of low rotating speeds as shown in FIG. 10.Accordingly, it becomes possible to execute effective motor control evenwhen the rotating speed is low. FIG. 10 shows the relationships of theDC voltage, duty ratio and the motor voltage to the number ofrevolutions when a converter capable of freely controlling the DCvoltage is used.

While the number of revolutions was taken along the abscissa in theexplanatory drawings of the controlling operations shown in FIG. 3, FIG.4, FIG. 9, and FIG. 10 above, similar graphs can be obtained even if themotor load or motor output is taken along the abscissa.

FIG. 11 shows a configuration of a DC voltage control circuit includinga duty ratio control circuit formed of a duty ratio command valuegenerator circuit 80, a proportional term 81, and an integral term 82for linearly outputting the DC voltage command value similar to thecircuit shown in FIG. 7. By using such a duty ratio control circuit, theDC voltage command value for keeping the duty ratio constant can becalculated. Even when the DC voltage control circuit shown in FIG. 11 isused, operations like those shown in FIG. 9 and FIG. 10 can beperformed.

The configuration of a motor controller according to another embodimentof the invention will be described with reference to FIG. 12 and FIG.13. FIG. 12 is an overall block diagram of the motor controller, andFIG. 13 is a block diagram of the DC voltage control circuit 11 shown inFIG. 12. The different point of the present embodiment from theembodiment shown in FIG. 1 lies in the DC voltage control circuit 11,namely, in the fact that the duty ratio signal and a speed deviationsignal within the speed control circuit 12 shown in FIG. 12 are used forselection in the DC voltage detector circuit 97.

Operations of the selector circuit 110 shown in FIG. 13 will bedescribed with reference to FIG. 3. The selector circuit 110, when theduty ratio has reached 100% and the speed deviation is tending toincrease the duty ratio still further, switches the output of the DCvoltage detector circuit 97 to increase the DC voltage. Conversely, whenthe duty ratio has lowered to 60% and the speed deviation is tending todecrease the duty ratio still further, it switches the output of the DCvoltage detector circuit 97 to decrease the DC voltage. Thereby, themotor controller of the present embodiment operates as shown in FIG. 3.

When the motor controller shown in FIG. 1 is used, since the selectorcircuit 93 takes only the duty ratio signal as the criterion for itsselection, it would switch the DC voltage even when the motor load andmotor output are balanced at the duty ratio of 100% or 60%.

The present embodiment is improved in view of the above described point.Namely, rather than detecting the duty ratio signal, it detects a signalto determine whether the motor load and the motor output are balanced, aspeed deviation signal in the present case, so as to prevent uselessswitching over of the DC voltage value. Although the speed deviationsignal is detected in the present embodiment, another signal may be usedprovided that it indicates a balanced state between the motor load andthe motor output.

While, in this embodiment, the DC voltage detector circuit 97 is adaptedto select one of the DC voltages, it may be adapted to provide aplurality of DC voltage command values and to select one DC voltagecommand value therefrom.

A motor controller according to still another embodiment of theinvention will be described with reference to FIG. 14 and FIG. 15. FIG.14 shows a DC voltage pulsation correcting motor controller which isformed of the motor controller shown in FIG. 1 with a DC voltagepulsation correcting circuit 10 added thereto. FIG. 15 is a drawingexplanatory of the operation of the DC voltage pulsation correctingmotor controller of FIG. 14.

Each circuit of the DC voltage pulsation correcting motor controllershown in FIG. 14 operates in the same manner as in the first embodimentshown in FIG. 1, except for the DC voltage pulsation correcting circuit10. The DC voltage pulsation correcting circuit 10 detects pulsatingcomponents in the DC voltage and multiplies the duty ratio signalgenerated in the speed control circuit 7 by a pulsating signal ofopposite phase to the detected pulsating components to thereby generatea correcting duty ratio signal.

FIG. 15 shows changes with time in the duty ratio when the DC voltagepulsation correction was made. In FIG. 15, the abscissa represents thetime and the ordinate represents the DC voltage, the duty ratio, and thecorrecting duty ratio. It is known that the correcting duty ratio variesin the opposite phase to the pulsating components of the DC voltage.

According to this embodiment, even if there exist pulsating componentsin the DC voltage, motor control not affected thereby can be executed.In this system, however, the DC voltage control circuit 9 must becontrolled with the duty ratio kept below 100%.

The configuration of an air conditioner controller, to which the motorcontroller of the present invention is applied, is shown in FIG. 16.This embodiment relates an inverter air conditioner for detecting theroom temperature and for controlling the room temperature to maintain aset temperature.

The air conditioner controller comprises a room temperature sensor 203for detecting the room temperature, a temperature control circuit 202for calculating a rotation command value for a compressor 200 to bringthe temperature deviation between the room temperature detection valueand the room temperature setting value to zero, a compressor rotationcontrol circuit 201 responsive to the rotation command received from thetemperature controller 202 for controlling the number of revolutions ofthe compressor 200, a refrigerating cycle control circuit 206 fordetecting the rotation command value and for calculating and outputtingcontrol signals for controlling an outdoor fan 204, an indoor fan 210,and an expansion valve 208 constituting the refrigerating cycle, andcontrol circuits (an outdoor air quantity control circuit 205, an indoorair quantity control circuit 209, and an expansion valve opening controlcircuit 207) responsive to a control signal from the refrigerating cyclecontroller 206 for controlling each of the constituents of therefrigerating cycle (the outdoor fan 204, the indoor fan 210, and theexpansion valve 208).

The compressor rotation control circuit 201 is a motor controllerresponsive to the rotation command value from the temperature controlcircuit 202 for controlling the speed of the motor directly coupled withthe compressor, to which the motor controller of the above describedembodiment is applied.

The outdoor air quantity control circuit 205 and the indoor air quantitycontrol circuit 209 are also constituted, like the compressor rotationcontrol circuit 201, of motor controllers for controlling the speeds ofthe motors directly coupled with the outdoor fan and the indoor fan.Signals output from the refrigerating cycle control circuit 206 arerotation command signals for the indoor fan and the outdoor fan.

The expansion valve opening control circuit 207 is directly coupled withthe expansion valve 208 and operates as a controller of a step motor forregulating the opening of the expansion valve by generating a stepsignal in accordance with an opening signal output from therefrigerating cycle control circuit 206 to thereby drive the step motor.The expansion valve 208 is a motor-driven expansion valve whoseexpansion valve opening is changed in proportion to the angle ofrotation of the step motor.

The refrigerating cycle controller 206 calculates control signals forcontrolling the constituents of the refrigerating cycle (the outdoor fan204, the indoor fan 210, and the expansion valve 208) such that thenumber-of-revolutions command value as the output of the temperaturecontroller 202 becomes a preset value and outputs thenumber-of-revolutions commands and the opening command to the respectivecontrollers. The control signals for the constituents of therefrigerating cycle are calculated such that the refrigerating cycle asa whole operates at the highest efficiency.

The value of the number-of-revolutions command to be previously set inthe refrigerating cycle control circuit 206 is changed according tooperating conditions of the inverter air conditioner.

By using the air conditioner controller of the present invention,rotations of the compressor at excessively high speeds can be preventedand the service life of the compressor can be prolonged. Further, sincethe refrigerating cycle as a whole can be operated at the highestefficiency, the cooling and heating capacity is improved and electriccharges required for the operation can be saved.

The configuration of a converter module according to an embodiment ofthe present invention is shown in FIG. 17. This converter module isobtained by having a rectifier circuit, the converter circuit 2, theconverter control circuit 8, and the DC voltage control circuit 9described in the first embodiment integrally incorporated in a singlemodule. In this module, a step-up chopper is used.

The converter circuit is formed of a rectifier circuit 101, a reactor102, a transistor 104, a diode 103, and a smoothing capacitor 105, ofwhich the semiconductor devices of the rectifier circuit 101, transistor104, and the diode 105 are modularized.

The converter control circuit 106 has the same function as the convertercontrol circuit 8 shown in FIG. 2. The selector circuit 108 selects oneof the DC voltage values of the DC voltage detector circuit 107 inaccordance with an external signal. Further, the selector circuit 110selects one of the DC voltage command values of the DC voltage commandcircuit 109 in accordance with an external signal.

By the present embodiment, a converter device capable of controlling DCvoltage can be easily fabricated in a compact form.

According to the motor controller of the present invention, as describedin the foregoing, it is possible to decrease losses incurred in themotor, inverter, and converter by the use of simple structures and toeffectively run the controller. Further, since the DC voltage can bevaried in accordance with the number of revolutions of the motor, onecontroller can support an operation ranging from a low speed operationto a high speed operation. In other words, even several types of motorsof different motor design can be controlled by one controller andoperated so as to provide high efficiency at all times. Further,correction for the pulsation in the DC voltage can be easily carried outand stabilized motor speed control can be achieved.

When the present motor controller is applied to an inverter airconditioner, highly efficient refrigerating cycle control can beperformed and the cost of electricity can be reduced.

Still further, by modularizing the converter circuit in the motorcontroller of the invention, a compact motor controller can be easilyfabricated.

We claim:
 1. An electric device comprising: a motor; a compressor drivenby said motor; and a control device that controls said motor inaccordance with a state of a load of said motor; wherein said controldevice changes a first DC voltage for said motor into a second DCvoltage for said motor when a number of revolutions of said motorbecomes a predetermined state in accordance with the state of the loadof said motor.
 2. An electric device according to claim 1, wherein saidelectric device is an inverter air conditioner.
 3. An electric deviceaccording to claim 1, wherein said control device includes an inverterwhich is always pulse width modulation controlled.
 4. An electric devicecomprising: a motor; a compressor driven by said motor; and a controldevice that controls said motor in accordance with a state of a load ofsaid motor; wherein said control device changes a first DC voltage forsaid motor into a second DC voltage for said motor when a duty ratio ofsaid motor becomes a predetermined state in accordance with the state ofthe load of said motor.
 5. An electric device according to claim 4,wherein said electric device is an inverter air conditioner.
 6. Anelectric device according to claim 4, wherein said control deviceincludes an inverter which is always pulse width modulation controlled.7. A motor controller comprising: a converter circuit including arectifier circuit for converting AC power to a DC voltage, a smoothingcircuit, and a chopper circuit for controlling said DC voltage byutilizing a switching operation and the energy storing effect of aninductance; a motor drive device including an inverter circuit connectedto the output of said converter circuit for controlling a motor; aconverter control circuit for controlling the switching operation ofsaid chopper circuit; an inverter control circuit for controlling theswitching operation of said inverter circuit for driving said motor; aspeed detector circuit for detecting a position of the rotor of saidmotor for calculating the speed value of said motor; a speed controlcircuit responsive to said calculated speed value and a speed commandvalue for performing speed control of said motor through said invertercontrol circuit; and a DC voltage control circuit responsive to theoutput signal of said speed control circuit for controlling said DCvoltage through said converter control circuit; wherein said DC voltagecontrol circuit, when the output of said speed control circuit reaches apredetermined value, outputs a signal to said converter control circuitto cause said DC voltage to increase in accordance with a state of aload of said motor.
 8. A motor controller according to claim 7, whereinsaid inverter circuit is always controlled by pulse width modulationcontrol.
 9. Motor controller comprising: a converter circuit including arectifier circuit for converting AC power to a DC voltage, a smoothingcircuit, and a chopper circuit for controlling said DC voltage byutilizing a switching operation and the energy storing effect of aninductance; a motor drive device including an inverter circuit connectedto the output of said converter circuit for controlling a motor; aconverter control circuit for controlling the switching operation ofsaid chopper circuit; an inverter control circuit for controlling theswitching operation of said inverter circuit for driving said motor; aspeed detector circuit for detecting a position of the rotor of saidmotor for calculating the speed value of said motor; a speed controlcircuit responsive to said calculated speed value and a speed commandvalue for performing speed control of said motor through said invertercontrol circuit; a DC voltage control circuit responsive to the outputsignal of said speed control circuit for controlling said DC voltagethrough said converter control circuit; and a DC voltage pulsationcorrecting circuit for detecting pulsating components of said DC voltagefor changing the input signal to said inverter control circuit inaccordance with the pulsating components.
 10. A motor controllercomprising: a converter circuit including a rectifier circuit forconverting AC power to a DC voltage, a smoothing circuit, and a choppercircuit for controlling said DC voltage by utilizing a switchingoperation and the energy storing effect of an inductance; a motor drivedevice including an inverter circuit connected to the output of saidconverter circuit for controlling a motor; a converter control circuitfor controlling the switching operation of said chopper circuit; aninverter control circuit for controlling the switching operation of saidinverter circuit for driving said motor; a speed detector circuit fordetecting a position of the rotor of said motor for calculating thespeed value of said motor; a speed control circuit responsive to saidcalculated speed value and a speed command value for supplying saidinverter control circuit with a duty ratio signal to cause the speeddeviation to approach zero; and a DC voltage control circuit connectedto receive said duty ratio signal, and including a DC voltage commandvalue generator circuit for generating a DC voltage command value and aDC voltage detector circuit for detecting a DC voltage corresponding tothe output of said converter circuit, a selector circuit for selectingthe DC voltage command value or the DC voltage detection value so thatsaid duty ratio signal takes on a value within a predetermined range,and a circuit for generating a current command value to cause thedeviation of the DC voltage detection value from the DC voltage commandvalue to approach zero and for outputting the current command value tosaid converter circuit.
 11. A motor controller according to claim 10,wherein said speed control circuit further outputs a signal representingsaid speed deviation and inputs the same to said DC voltage controlcircuit.
 12. A motor controller according to claim 10, wherein said DCvoltage control circuit, when said duty ratio signal reaches the upperlimit value or the lower limit value of said predetermined range,generates a current command value for increasing or decreasing said DCvoltage.
 13. A motor controller according to claim 10, furthercomprising a DC voltage pulsation correcting circuit for detectingpulsating components of said DC voltage, for generating a correctingduty ratio signal by multiplying said duty ratio signal by a pulsatingsignal in opposite phase to said pulsating components, and for inputtingthe same to said inverter control circuit.
 14. An inverter airconditioner having: a rectifier circuit for converting AC power to a DCvoltage and a smoothing circuit; a power factor improving circuitincluding a step-up chopper circuit for controlling said DC voltage andcontrolling the power factor of the power supply to effect improvementthereof by utilizing a switching operation and the energy storing effectof an inductance; a motor drive device including an inverter circuitconnected to the output of said power factor improving circuit forcontrolling a motor; a chopper control circuit for controlling theswitching operation of said step-up chopper circuit; an inverter controlcircuit for controlling the switching operation of said inverter circuitfor driving the motor; and a speed control circuit for controlling thespeed of said motor by using said inverter control circuit in accordancewith a speed command value coming from a temperature control circuit ofsaid air conditioner, said inverter air conditioner comprising a DCvoltage control circuit detecting the output signal of said speedcontrol circuit for causing the DC voltage to rise when said outputsignal reaches a predetermined upper limit value and causing the DCvoltage to fall when the output signal reaches a predetermined lowerlimit value.
 15. An inverter air conditioner according to claim 14,wherein the output signal of said speed control circuit is a duty ratiosignal.